Glossary

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A pipe inserted in the borehole to stabilize the hole when using small diameter drill string, when recovering a stuck drill pipe, or when retracting a drill string to change bits or to re-tool. Washover pipes may also be used to stablilize the bore when drilling in difficult unstable formations.

Water Jetting

Internal cleaning mechanism of the cutterhead in which high-pressure water is sprayed from nozzles to help remove cohesive soils.

Wireline

Surface system consisting of a grid of energized wire coil, which in combination with a downhole survey probe, tracks the location of the drill string.

Working Shaft

A general term applied to the more specific description of thrust or reception pits.